Apparatus for applying emission material to cathodes



March 20, 1951 w. P. ZABEL APPARATUS FOR APPLYING EMISSION MATERIAL TOCATHODES Filed Dec. 22, 1948 lnven bov'.

WiLLiam P. ZabeL,

His A t' L-orneg.

Patented Mar. 20, 1951 APPARATUS FOR APPLYING EMISSION MATERIAL TOOATHODES William P. Zabel, Cleveland Heights, Ohio, assignor to GeneralElectric Company, a corporation of New York Application December 22,1948, Serial No.- 66,643

My invention relates to the application of electron emission material tothe filamentary cathodes of electric discharge lamps and similardevices. More particularly my invention relates to apparatus forflooding the complex coils of filamentary cathodes with a liquidcontaining the electron emission material and thereafter removingsubstantially all the excess liquid therefrom.

, To assure the most efficient and satisfactory operation of filamentarycathodes of discharge devices, it is imperative that a relatively large.quantity of the emission material be carried by the cathode and thatthe emission material be tenaciously retained by and uniformlydistributed over said cathode. An object of my invention is accordinglyto provide apparatus which will completely fill the smaller intersticesof the cathode as, for instance, the primary coils of a coiled-coilcathode, and at the same time avoid the formation of heavy incrustationsand bridges of emision material on the surface and more widely spacedportions of said cathode as, for instance,

on the secondary coils of said coiled-coil cathode,

Other objects and advantages of my invention will appear from thefollowing detailed description of a species thereof, and from theaccompanying drawing.

In the drawing, Fig. 1 'is a side elevation of one species of apparatuscomprising my invention with a portion broken therefrom, and with ashowing of the dipper thereof in dot-dash lines in its operativeposition with relation to the cathode; Fig.2 is a plan view of thedipper, the cup and certain of the associated operating parts of theapparatus; and Fig. 3 is a perspective view on a larger scale of theapplicator of the apparatus in operative arrangement to the cathode of adischarge lamp mount.

2 Claims. (01. 91-47) The apparatus of my invention occupies a' positiondirectly below that occupied by the oathode I throughout the completecycle of operation thereof, and in said cycle carries a quantity of aliquid containing the emission material up into engagement with saidcathode I. function of the apparatus is that it floods a specificportion of the cathode I with the liquid containing the emissionmaterial, thereby effecting the distribution thereof over a definiterelated portion of said cathode I and, in the withdrawal thereof,effects a pulling or draining of the excess liquid from said cathode I.As shown in the drawing, the cathode I may be one permanently attachedto the leading-in wires 2 and. 3 of a mount 4 for a discharge device andis preferably, although not necessarily, stretched linearly so Aparticular widely spaced.

that the larger secondary coils 5 thereof are The apparatus can bereadily combined with other apparatus, such as that disclosed in U. S.Patent 2,380,742, Flaws, for automatically manufacturing the mount 4,and in such a combination can belocated at one of the work stations intowhich the mount 4 is advanced in its regular course of movement. Thejaws 6 and 1 support the mount 4 in position and together therewitharrange the cathode at a definite position and orientation with respectto the apparatus of my invention.

At the start of the cycle of operation, the applicator 8, which is anelement of the troughshaped dipper 9, is located within the cup I0 andis completely submerged and flooded by the main supply of the liquidsuspension of emission material. Subsequent operations of the apparatusraise the dipper 9 vertically out of the cup ID to operative relation tothe cathode I (to the position shown in dot-dash lines), and then returnsaid dipper 9 to its original position within the cup II] and theliquid. This manipulation of the dipper 9 accounts for the completecycle of operation of the apparatus and is brought about by the verticalmovements of the operating rod I I in the manner of other cam-actuatedoperating means at other work stations of apparatus like that disclosedin U. S. Patent 2,380,742, Flaws, hereinbefore referred'to.

The movement of the dipper 9, which is attached to the operating rod IIby rod I2 and arm I3, effects a thorough agitation of the main supply ofthe liquid containing the emission material in its passage from and theninto said liquid in said cup II], which is mounted on the stud I4extending from the support bracket I5. Such. a manner of operation keepsthe emission material, which is in the form of a finely ground solid(usually alkaline earth carbonates), in a homogeneous mixture with theother components of the liquid (usually nitrocellulose and amyl acetate)and causes said supply to thoroughly wash all portionsv of the dipper 9and the applicator 8 so as to prevent the formation of incrustations andsolid gatherings of the emission tition I6 bridging the ring I1, andpasses through the opening in said ring I! and the opening I8 in thebottom of said dipper 9 to the main supply Within the cup Ill. Thereverse downward movement of the dipper 9 causes a reverse flow of theliquid and a spilling of said liquid into the top of the dipper 9 whenit finally becomes submerged therein.

The application of the emission material to the cathode I occurs whenthe dipper 9 is raised sufficiently so that the larger secondar coils 5of the said cathode I are located within the openended trough I9 runningthe length of the applicator 8 and almost entirely submerged within thepool of liquid contained therein. The movement is terminated whensecondary coils 5 of the cathode I rest upon the longitudinallyextending ridge 20 along the bottom of the applicator 8 and are pushedup slightly from their normal position. The restricted length of theapplicator 3 confines the distribution of the emission material to theexterior surfaces of the secondary coils 5 of the cathode I. However,the full length of the oathode I is comprised of small primary coils offilamentary wire into which the liquid is drawn by capillary action soas to travel therealong almost to the leading-in wires 2 and 3.

Both the design of the applicator and the viscosity of the liquidcontaining the emission material are responsible for the distribution ofsaid emission material over the cathode I since excessively thin liquidtravels farther from the applicator 8 along the primary coils thandesired. To this end, it is desired that the applicator 8 and liquid beso correlated in size and viscosity as to carry the emission materialonly to those portions of the cathode I which are adapted to beadequately heated by the passage of current between the leading-in wires2 and 3 in a subsequently occurring manufacturing operation and therebconverted to oxides of a suitable character and emissivity. The lateralproportions of the applicator 8 and viscosity of the liquid are also ofmajor importance to the proper application of the emission material andare such that sufficient liquid is retained in the applicator 8 byadhesion and cohesion after it is completely withdrawn from the mainsupply of liquid to flood the full periphery of the cathode I. It istherefore preferable that the depth of liquid within the applicator 8 begreater than the diameter of the larger secondary coils 5 of the cathodeI; however, it may be slightly less than said diameter and relianceplaced upon capillary attraction to pull said liquid through the coilsand up and over the top thereof. proper immersion of the cathode I isgiven by the final upward movement of the applicator 8 which causes allof the secondary coils 5'to bear against the ridge 20, even thoughcertain of said coils 5 may be slightly out of proper alignment with theothers.

The subsequently occurring downward movement of the dipper 9 separatesthe liquid contained in the applicator 8 from the cathode I,

and in so doing pulls away from the cathode substantially all of theliquid not confined within the primar coils and wetting the surface ofthe Further assurance of the i cathode I. This forceable drainingfunction of the applicator 8 is effected by the tendenc of the liquid tocling to said applicator 8, possibly because of capillary attraction inthe V-shaped channels on the sides of the ridge 20 and cohesion of theliquid therein. In this manner, substantially all of the excess liquidis withdrawn from the cathode I and there is substantially no creepingof liquid over the cathode I to the lower part thereof during theinterval immediately following, thereby preventing a heavy surfacincrustation of the emission material on said lower portions.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. Apparatus for applying electron emission material to a coiledfilamentary cathode comprising a cup for holding a pool of a liquidcontaining the emission material, a movable applicator in the form of ahorizontally disposed open-ended trough having a ridge extendingcentrally and longitudinally along the bottom thereof, means forsupporting the cathode in a horizontal position above said cup and withits longitudinal axis parallel to and in alignment with the longitudinalaXis of said applicator, and means for supporting the applicator in ahorizontal position and carrying it upward toward the cathode supportmeans from a normal immersed position within the cup to a positionsurrounding the cathode and with the said ridg pressed firmly againstthe coils of the cathode so as toapply the emission material to thecathode before it drains out of the trough and for returning saidapplicator to its position within the cup so as to effect a withdrawalof .the excess liquid from said cathode.

2. Apparatus for applying electron emission material to a coiledfilamentary cathode comprising a cup for holding a pool of a liquidcontaining the emission material, a movable applicator in the form of ahorizontall disposed openended trough having an inverted V-shaped bottomdefining a longitudinally extending ridge therein, means for supportingthe cathode in a horizontal position above said cup and with itslongitudinal axis parallel to and in alignment with the longitudinalaxis of said applicator, and means for supporting the applicator in ahorizontal position and carrying it upward toward the cathode supportmeans from a normal immersed position within the cup to a positionsurrounding the cathode and with the said ridge pressed firmly againstthe coils of the cathode so as to apply the emission material to thecathode before it drains out of the trough and for returning saidapplicator to it position within the cup so as to eiTect a withdrawal ofthe excess liquid from said cathode. .WILLIAM P. ZABEL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,363,055 Flaws, Jr l Nov. 21,1944.- 2,422,457 Zabel June 17, 1947

